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Under the car on our account they have the key card as an option to buy. This should not be there for the older Model Xs but it is. The "They" he refers to is whoever at Tesla who allows older Model X owners the option to buy the key card because it is listed as key on the account page.
According to a Tesla rep at one of their showrooms, a technician can setup a keycard for a PRX-21 (prefresh 2021 or earlier). However, I do cast doubt on if this is actually true or not